Phenol adsorption rates from

Figure 8. Adsorption rates from phenol and p-toluene sulfonate mixtures (O)...

Phenol and dodecyl benzene sulfonate are two solutes that have markedly different adsorption characteristics. The surface diffusion coefficient of phenol is about fourteen times greater than that for dodecyl benzene sulfonate. The equilibrium adsorption constants indicate that dodecyl benzene sulfonate has a much higher energy of adsorption than phenol (20,22). The adsorption rates from a mixture of these solutes can be predicted accurately, if (1) an adequate representation is obtained for the mixture equilibria, and (2) the diffusion rates in the solid and fluid phases are not affected by solute-solute interactions. 

The experimental and predicted profiles for adsorption from a mixture 5 x 10 H phenol and 5 x 10 H dodecyl benzene sulfonate are shown in Figure 15. The rate of adsorption of dodecyl benezene sulfonate is faster than predicted, and for phenol, the rate is slower than predicted. However, the shape of the predicted profiles for both solutes closely parallel the experimental curves. Similar trends may be noted in Figure 16 for the adsorption rates from a 10 4 H phenol and 10 4 H dodecyl benzene sulfonate mixture. The mixture equilibrium data for these solutes have been correlated satisfactorily. Thus, it would appear that solute-solute interactions are affecting the diffusional flux of each solute. Moreover, from Figure 17 for the total concentrations, it may be seen that the interaction effects are mutually compensating. The total concentration profiles for both... 

As seen from Table 2, phenol, j>-toluene sulfonate and 2 bromophenol have similar adsorption rate characteristics. The equilibrium data for these solutes indicate that phenol and p-toluene sulfonate have similar energies of adsorption (24), as indicated by the constant b in the component isotherm (qe Qbx,ce/ (1 + bLCe) -bromophenol and dodecyl benzene sulfonate are adsorbed more strongly than phenol (22). 

The experimental and predicted profiles for the adsorption rates of phenol and -bromophenol from an equimolar mixture of concentration 5 x 10-4 M are shown in Figure 12. The predicted profile for j>-bromophenol is in excellent agreement with the experimental data. However, for phenol there is some deviation after the Initial time period. The experimental adsorption rate for phenol appears to be faster than predicted for about 60 minutes after the first 15 minutes. Thereafter, the rate Is slightly slower than predicted. From an examination of the binary equilibrium data, this deviation may be attributed to the Inadequate correlation of the mixture equilibrium data in this region. The predicted and experimental total concentration profiles are shown In Figure 13. Initial concentrations of 2.5 x 10 4 M for phenol, and 5 x 10 4 M for j>-bromphenol were used in another rate study, the data from which are shown in Figures 13 and 14. The experimental and predicted curves are in fair agreement. 

Recently, the use of sulfolane solvent allowed better kinetic control of the oxidation chain, with an increase of the selectivity to 80% or greater, at ca 8% benzene conversion. The by-products were catechol (7%), hydroquinone (4%), 1,4-benzo-quinone (1%) and tar (5%) [53, 54]. According to these authors, a rather stable complex, formed by hydrogen bonding with sulfolane, promoted desorption and hindered the re-adsorption of phenol, protecting it from consecutive oxidation (Equation 18.7). Actually, the rate of oxidation of phenol in the presence of sulfolane was only 1.6 times that of benzene, while it was 10 times higher in the presence of acetone. 

In this work, the efTect of anodic oxidation treatments on activated carbon fibets (ACFs) was studied in the context of Cr(Vl), Cu( II), and Ni( II) ion adsorption behaviors. Ten wt% phosphoric acid and sodium hydroxide were used for acidic and basic electrolytes, respectively. Surf properties of the ACFs were determined by XPS. The specific surface area and the pore stnicture were evaluated from nitrogen adsorption data at 77 K. The heavy metal adsorption rates of ACFs were measured by using a UV spectrometer and 1C P. As a result, the anodic treatments led to an increase in the amount of total acidity by an increase of acidic functional groups such as carboxyl, lactone, and phenol, in spite of a decrease in specific surface area, due to the pore blocking by increased acidic functional groups. 

In addition to pore structure, tlie surface chemistry of the adsorbent may have a strong influence on the adsorption of aromatic compounds. Fig. 7 (from [48]) shows that the Langmuir adsorption capacity of phenol is dependent tai the concentration of acidic surface oxides, as defined by Boehm [49]. Furthermore, for acidic and basic species, the effect of the adsorbent s surface charge combined with that of the pH of the solution is extremely important because it determines the nature of the forces (attractive/repulsive) between the adsorbate and the adsorbent surface. For cationic dyes, adsorption is promoted when the surface charge is negative adsorption capacities are 1.7 to 2.3 times higher at basic pH and adsorption rates are doubled [50]. 

The results showed that oxidation kinetics were independent of the undissolved substrate but were dependent on its concentration in solution. Reaction rate increased at alkaline pH, due to a lower phenol adsorption onto the catalyst surface which reduced further oxidation reactions. Additional tests showed that oxygen from the surface contacting air did not represent the limiting reagent in our system. Negligible variations of the rate of phenol production were obtained (values ranging between 0.13 and 0.18 mg/dm -min in the first 100 min) by changing the catalyst amount from 0.1 to 1 g/dm. ... 

Plant uptake is one of several routes by which an organic contaminant can enter man s food chain. The amount of uptake depends on plant species, concentration, depth of placement, soil type, temperature, moisture, and many other parameters. Translocation of the absorbed material into various plant parts will determine the degree of man s exposure—i.e., whether the material moves to an edible portion of the plant. Past experience with nonpolar chlorinated pesticides suggested optimal uptake conditions are achieved when the chemical is placed in a soil with low adsorptive capacity e.g., a sand), evenly distributed throughout the soil profile, and with oil producing plants. Plant experiments were conducted with one set of parameters that would be optimal for uptake and translocation. The uptake of two dioxins and one phenol (2,4-dichlorophenol (DCP)) from one soil was measured in soybean and oats (7). The application rates were DCP = 0.07 ppm, DCDD 0.10 ppm, and TCDD = 0.06 ppm. The specific activity of the com-... 

The USEPA surveys identified four resin adsorption systems in the pesticide industry [7]. Phenol, pesticide, and diene compounds are all effectively removed by these systems. At least one system realized a significant product recovery via regeneration and distillation. The design surface loading rates vary from 1.0 to 4.0 gpm/ft with empty bed contact times of 7.5 to 30 minutes. 

In general, there is no correspondence between the value of K obtained from the fit of kinetic data through Eqs. (la)—(If) and dark adsorption measurements. The degradation rate of phenol (ph, poorly adsorbed) and nonylphenol (nph, strongly adsorbed) differs only by a factor of 3 [23], Because it was demonstrated that the aromatic moiety is more susceptible of attack than the aliphatic chain, A lh would be almost identical in the two cases. Owing to the large ratio of A npij/T ph (>>3), it follows that the LH equation is inadequate. 

Adsorption equilibria for the systems phenol-p-toluene sulfonate, phenol-p-bromophenol and phenol-dodecyl benzene sulfonate are shown in Figures 5, 6 and 7. In these figures, the ratio of the observed equilibrium values and computed values from equation (14) are plotted against the equilibrium liquid phase concentration of the solute in the mixture. It is seen that most of the data points are well within a deviation of 20%. The results for these diverse solute systems indicate that equation (14) is suitable for correlating binary equilibrium data for use in multicomponent rate models. 

Figure 10. Total concentration rate profile for adsorption from phenol and p-toluene sulfonate mixtures fQ) experimental data of Figure 8, (O) experimental data of Figure 9, (-------------------------) predicted rate...

Figure 17. Total concentration rate profile for adsorption from phenol and dodecyl...

Zeolite polarity and reaction rate The competition between sulfolane, PA and product molecules for the adsorption on the active protonic sites is sufficient enough to explain the differences in reaction orders and catalyst stability and selectivity between PA transformation in sulfolane and in dodecane. However, the competition for the occupancy of the zeolite micropores plays a significant role as well. This was demonstrated by studying a related reaction the transformation of an equimolar mixture of PA with phenol in sulfolane solvent on a series of H-BEA samples with different framework Si/Al ratios (from 15 to 90).[49] According to the largely accepted next nearest neighbour model,[50,51] the protonic sites of these zeolites should not differ by their acid strength, as furthermore confirmed by the... 

Advantage can be drawn from the positive effect of phenol on PA transformation into p-HAP to improve the yield and selectivity of p-HAP production.[82 84] Thus, with a HBEA zeolite the yield and selectivity for p-HAP passes from ca. 5 and 28 % respectively with cumene solvent to 24 and 60% with phenol as a solvent .[84] Again sulfolane was shown to have a very positive effect on the selectivity for p-HAP and limits the catalyst deactivation. To explain these observations as well as the effect of P and PA concentrations on the reaction rates, it was proposed that sulfolane plays two independent roles in phenol acylation solvation of acylium ion intermediates and competition with P and PA for adsorption on the acid sites.1831... 

---